The man stood shouting at me may well have been the first victim of London's long-dreaded card clash - his usual touch of his Oyster card as he entered Canary Wharf tube station actually charging the amount to his Mastercard
To his credit, the commuter was less worried about the £2.10 charge than the inconvenience in rectifying the problem, and he was no doubt impressed at the sheer number of well-dressed Transport for London senior staff gathered in the station as he sought out someone to tell.
That's because it was the press conference to launch contactless payment across London's travel network, and the first person he chose to march up and showed his ire to was from TechRadar.
Sometimes you have to go looking for stories, and other times they just fall in your lap.
"I'm angry that I'm being charged for this," he said. The problem was, of course, that he keeps his Oyster card, complete with a monthly travelcard in the same wallet as his Mastercard. He rightly points out that he's almost certainly in the majority in doing this.
It was certainly not a highlight for TfL's team, but an elephant in the room loudly trumpeting its displeasure did create an opportunity to talk about both the huge benefits that contactless payments bring, and a layer of inconvenience for many of its most loyal commuters.
For the overwhelming majority of people who use the tube, the ability to pay for your journey through your credit and debit card (assuming they have pay wave / NFC / contactless technology) and to have the amount capped so that you will only spend the minimum you have to in a day or week is a welcome one.
Crowds of tourists, thousands of occasional commuters and of course the forgetful or those that mistrust Oyster will join a system that has been planned over years and, from our early experience, is an impressive and seamless new feature of London's transport.
And blaming card clash itself on TfL is a bit like blaming Manchester United for England's national football team woes - it's a high-profile and recent part of the problem but not the root cause.
What is likely to rankle most is not the constant barrage of 'beware card clash' messages or even the occasional and, hopefully rare, times when we find our cards debited. It's that card clash is for some reason considered the problem of the consumer.
Let's get this straight - Paywave and NFC are systems that exists to make things more convenient for the consumer, and we all get why having one card is more convenient than 20.
But if we have more than one NFC-enabled card - which increasingly we will have - then, according to our banks (and now TfL) we should be keeping them all in different places.
When we predicted the death of the wallet, it was with the hope that it would be a digital nirvana, not a world where you have to keep your credit card in your hatband, your debit card in your shoe and your oyster card in your jacket pocket.
This is not a problem of our making, and having to find a solution for it is simply unacceptable.
That it's the first step in a journey of a thousand miles is something we can all accept, but when you stand on our toe on that first step and blame us for the inconvenience, it certainly makes the trip less pleasant.
The man behind TfL's new scheme Shashi Verma is a very nice chap - and his passion for this new offering and its benefits do both him and his company a credit.
And yet throughout an interesting chat about contactless payment, Vema was adamant that it's not his problem but ours.
"It's an issue everywhere in the payments world," he told TechRadar. "The Oyster card when it first arrived was the only contactless card available but it's now a problem for the whole industry.
"The point here is that it's a fact of life."
Of course, wearables and other contextual devices may solve the problem by working out where we are and what 'card', digital or otherwise, we want to be using.
But in the meantime we're being told that the only people to blame are us for deciding to keep our cards in one place and the old tech of NFC that can't differentiate between different cards.
It's an inelegant solution, a baffling mis-step, and blaming us is frankly insulting.
But we're just going to have to put up with it. And as for that first victim - TfL will no doubt ensure that he is refunded the fare - and he was kind enough to drop us a line.
"If I can totally replace Oyster card with one designated contactless bank cards and this would not clash with my other bank cards than, I would see the benefit of the new system."
So say we all.